1. Field of the Invention
The present invention relates to a ranging apparatus that can be attached to an imaging apparatus having an autofocus adjustment function, a lens system provided with this ranging apparatus, and an imaging apparatus.
2. Description of the Related Art
The processing carried out by autofocus adjustment in an imaging apparatus can be broadly divided into two processes: a focus detection process and a focus adjustment process. In the focus detection process, a ranging apparatus that is separate from the imaging apparatus is used in order to obtain high precision imaged object information. This ranging apparatus uses the principal of triangulation ranging in order to carry out focus detection. The principle of triangulation ranging includes a passive-type in which focus detection is carried out using the light that an object emits and an active-type in which ranging is carried out by detecting the reflection of light that is projected from the apparatus side toward an object. In this case, in the focus adjustment process, the optical system is focused based on the result of the focus detection. In this manner, in order to detect object information with high accuracy in the autofocus adjustment of an imaging apparatus, it is necessary to provide a ranging system in addition to an imaging system. Thus, in an imaging apparatus, the condition occurs in which the size of the imaging apparatus overall becomes large due to mounting the ranging system that is separate from the imaging system.
Conventionally, in order to resolve such a condition, a ranging-photometric apparatus has been proposed in which a ranging sensor and a photometric sensor are disposed on the same substrate and a plurality of independently provided ranging lenses and photometric sensors are integrally formed (refer, for example, to Japanese Patent Laid-Open No. 2004-12863). Note that a ranging optical system that includes ranging lenses is used as an imaging system and a photometric optical system that includes photometric lenses is used as a non-imaging system. According to this ranging-photometric apparatus, even if the ranging optical system and the photometric optical system are formed in one apparatus, high accuracy ranging and photometry become possible, and down-sizing and cost reductions can be implemented.
In the conventional technology described above, downsizing is implemented by providing a ranging apparatus (or photometric apparatus) that alleviates optical restrictions that occur because the ranging lenses and the photometric lenses are an integral structure and the restrictions due to the necessary angle of view of the photometric lenses with respect to the ranging lenses. In addition, the accuracy of the ranging and the photometry is also realized by reducing the restrictions that accompany downsizing. In this connection, the accuracy of the ranging apparatus must be compatible with the focus accuracy that is required on the zoom lens side of the imaging apparatus on which the ranging apparatus is mounted. However, in a ranging apparatus that uses this conventional technology, satisfying ranging specifications that are compatible with the focusing accuracy required on this zoom lens side is not easy.
In consideration of such circumstances, the present invention provides a ranging apparatus that satisfies ranging specifications that are compatible with the focus accuracy required on the zoom lens side of an imaging apparatus.